Mireille Lekimme

The pathology of Psoroptes ovis infestation in cattle with a special emphasis on breed difference

In cattle, infestations with P. ovis are responsible for a severe dermatitis. The disease is very common in some breeds of beef cattle whereas dairy cattle such as Frisian Holstein are considered as resistant. In order to investigate the factors responsible for this marked breed susceptibility, the immune response to P. ovis under experimental and field conditions has been studied using serology, lymphocyte transformation assay, intradermal tests and passive cutaneous anaphylaxis in susceptible Belgian White and Blue (BWB) and resistant Frisian Holstein (FH) cattle. The results of published studies are reviewed in this paper; original data on specific hypersensitivity reactions to P. ovisare also presented. The use of a sandwich ELISA allowed the detection of specific antibodies as early as 7 days post-infestation and very high titres were observed. There was a clear positive correlation between the antibody titre and the extent of lesions. This antibody response was associated with a marked in vitro lymphocyte proliferation but there was no difference between susceptible and resistant cattle. The passive cutaneous anaphylaxis test revealed the presence of specific Ig E in actively infested animals irrespective of the breed. Specific Ig E were detected fairly late during the course of an experimental infestation with P. ovis. The intradermal injection of P. cuniculi antigenic extract induced an immediate reaction in all animals including the controls; in contrast, a delayed hypersensitivity reaction was observed in infected BWB animals only. It is concluded that immunological as well as non-immunological factors may be responsible for the breed related susceptibility or resistance to P. ovis.

Failure of injectable ivermectin to control psoroptic mange in cattle

PSOROPTIC mange is a severe, debilitating skin condition affecting sheep, goats, rabbits, horses and cattle ([Soulsby 1982][1]). The causative mite, Psoroptes ovis , lives on the skin of the host, producing intense irritation ([Berriatua and others 2001][2]) that leads to marked economic losses and

In vitro tests for evaluation of the hatchability of the eggs of Psoroptes mites following exposure to acaricidal compounds.

Abstract.  Three in vitro assays for the evaluation of the hatchability of the eggs of the mite Psoroptes ovis (Hering) (Acari: Psoroptidae) are described. Preliminary trials showed that hatching occurs at very high rates when eggs are incubated under conditions of high humidity, on a liquid medium and in agarose dishes. These three protocols were compared, taking into account the ease of preparation, follow‐up and accuracy of counting. The best protocol was found to be the use of agarose dishes. It was accurate, easy to carry out and reproducible for further evaluation of existing or potentially new compounds against both adults and eggs of Psoroptes spp. The acaricidal properties of phoxim and amitraz were then evaluated against eggs and adults using the three protocols. Results showed that for both drugs, in vitro adulticidal activity was complete, whereas the in vitro ovicidal activity was only partial. Nevertheless, efficacy of amitraz against both adults and eggs was shown to be higher than that of phoxim.

Ultrastructural morphology of the male and female genital tracts of Psoroptes spp. (Acari: Astigmata: Psoroptidae).

The structure of the male and female genital systems of the astigmatid mite Psoroptesovis (Hering) is described. The male genital system is composed of a paired testis, fused at its proximal part, two vasa deferentia, an ejaculatory duct, into which a single accessory gland opens, and a copulatory organ. The testis is characterized by a peripheric syncytial cell surrounding spermatogonia, spermatocytes, spermatids and spermatozoa which are distributed regularly in the gonad according to the sequence of spermatogenesis. The female genital system consists of a copulatory pore (the bursa copulatrix), a seminal receptacle, paired ovaries and oviducts, a glandular uterus and an ovipositor which leads to the oviporus. Ovaries are composed of somatic cells, germ cells and a central cell, with a multilobular nucleus, connected to oocytes by a stalk. Similarities with other astigmatic mites belonging to Psoroptidia and Acaridia are also discussed.